This application is based on Application No. 2000-166142, filed in Japan on Jun. 2, 2000, the contents of which are hereby incorporated by reference.
This invention relates to a gas-insulated switchgear and, more particularly, to a gas-insulated switchgear having accommodated a switch within a hermetic vessel in which an electrically insulating gas is filled.
FIG. 3 illustrates in section a conventional gas-insulated switchgear disclosed in Japanese Patent Laid-Open No. 4-344108. In the figure, within a hermetic vessel 1 filled with an electrically insulating gas such as an SF6 gas, bus conductor bushings 2, disconnectors 3, interrupters 4 and cable bushings 5 are disposed in the named order and, inside of the outer frame 11 and in the front region of the front panel 6 of the hermetic vessel 1, bus conductors 7, cables 8, disconnector operating mechanisms 9 and interrupter operating mechanisms 10 are disposed.
With the structure as described above, the cable bushings 5 are disposed on the front panel 6 of the hermetic vessel 1 together with the disconnector operating mechanisms 9 as well as the interrupter operating mechanisms 10, so that the connection and disconnection of the cables 8 to the cable bushings 5 can be conveniently achieved from the front of the outer frame 11 in a manner similar to the maintenance and inspection of other devices such as the disconnector operating mechanisms 9.
However, in such the conventional gas-insulated switchgear, since the bus conductors 7 and the cables 8 are disposed on the front face of the hermetic vessel 1 and the height dimension of the outer frame 11 is determined by the layout of the bus conductor bushings 2 and the depth dimension of the outer frame 11 is determined by the layout of the bus conductors 7, the overall dimensions of the gas-insulated switchgear were large and the manufacturing cost was high.
Also, if an arc short-circuiting occurs around the bus conductor bushings 2 or the cable bushings 5, a sort of explosion phenomenon in which the arc energy causes a high temperature and a high pressure within a short time is induced at the front face of the outer frame 11.
Accordingly, one object of the present invention is to provide a gas-insulated switchgear free from the above-discussed problems of the conventional gas-insulated switchgear.
Another object of the present invention is to provide a gas-insulated switchgear that is significantly compact and inexpensive as compared to those of the conventional design, easy to handle and has a structure in which the explosive phenomenon as above discussed does not have much effects on the front face of the outer frame even upon the occurrence of the arc short-circuiting faults.
With the above objects in view, the present invention resides in a gas-insulated switchgear comprising a first hermetic vessel in which an electrically insulating gas is filled, at least one electric device selected from a group consisting of an interrupter, a disconnector, a grounding switch and a load switch contained within the hermetic vessel. The switchgear also comprises a cable bushing having a first end that passes through and is secured to a lower vessel wall of the first hermetic vessel and connected to the electric device and a second end that is connectable to a cable, and a solid-insulated bus conductor bushing mounted to the vessel wall of the hermetic vessel.
The gas-insulated switchgear may further comprise a second hermetic vessel disposed between the first hermetic vessel and the insulated bus conductor, containing a disconnector or a disconnector and a grounding switch together and filled with an electrically insulating gas, and an electrically insulated sealed terminal for connecting the electric device within the first hermetic vessel and the electric device within the second hermetic vessel.
The gas-insulated switchgear may further comprise a bus conductor compartment wall defining a bus conductor compartment externally separated above the vessel wall of the first hermetic vessel or the second hermetic vessel for accommodating the solid insulated bus conductors, and a flapper disposed to the bus conductor compartment wall for discharging an excessive internal pressure to the outside upon the internal pressure rise.
The gas-insulated switchgear may further comprise a grounding terminal disposed to the vessel wall of the hermetic vessels and connected to the electric device within the hermetic vessel and to which a test leads or a test cable can be connected at the time of withstand voltage test to apply a voltage.
The disconnector and the grounding switch may be a three-position switch that can take three positions of ON, OFF and GROUNDED according to the common operational mechanism.